1. Technical Field
The present disclosure relates generally to a surgical portal apparatus employing a system for maintaining a fluid-tight seal across a passageway for surgical instruments. In particular, the disclosure relates to a portal apparatus employing a variable diameter seal with a longitudinal displacement mechanism in communication with a power source for accommodating instruments of various sizes.
2. Background of Related Art
Surgical procedures such as laparoscopic, arthroscopic, and endoscopic procedures in general are termed minimally invasive at least in part because the incision required is relatively small, perhaps one inch in length or less. Small incisions are preferred because they are inherently less traumatic to the surrounding body tissue. Also, small incisions subject internal organs to a limited exposure to the contaminants in the outside atmosphere. Thus, small incisions enable shorter hospital stays and faster recoveries with less pain and scarring than is common with the larger incisions required for conventional surgery.
Endoscopic surgery is possible due in part to the availability of instruments designed specifically for this purpose. A trocar assembly, for example, may include a sharp trocar or obturator for creating a small incision, and a cannula assembly for providing a conduit through the incision once the obturator has been removed. A cannula is an elongated tube, typically 5 mm to 13 mm in diameter, which may be configured to have a distal end inserted into an internal body cavity adjacent an operative site. The body cavity is often inflated with an insufflation gas, carbon dioxide for example, to separate the body wall from vital organs. This provides a space where a surgeon may introduce viewing equipment or maneuver tools into position without damaging surrounding tissue. Various other instruments may then be inserted and withdrawn through the cannula for access to the working space and operative site. In order to fit through a cannula and enable a surgeon to manipulate tissue far removed from the incision, instruments adapted for endoscopic surgery typically include a long and narrow cylindrical shaft. The exact size and shape of the instrument shaft, however, may vary for the many instruments required for a single procedure.
Endoscopic procedures generally require that any instrumentation inserted into the patient's body be sealed, i.e. provisions must be made to ensure insufflation gasses, blood and other fluids do not escape the body through the cannula. Furthermore, a seal acts to prevent contamination of the body cavity by the outside environment. In the absence of such a fluid-tight seal, many of the attendant advantages of minimally invasive surgery are lost.
A dual seal system is commonly employed wherein a first seal is normally biased to a closed condition to seal the conduit in the absence of an instrument, and a second seal configured to form a fluid-tight interface with the shaft of an instrument. The second seal must be adaptable to accommodate the various instrument sizes and geometries. Often the second seal takes the form of a septum seal, which is a generally flat, elastomeric member having an orifice therethrough. The orifice may be sized such that the smallest instrument may not pass through the septum seal without engaging and forming a seal with the elastic material. The elasticity of the septum seal permits the orifice to expand to accommodate the largest instrument.
An aspect of concern in the use of such a septum seal is the contact pressure applied by the septum seal on the instrument shaft. If the contact pressure is insufficient, the insufflation pressure may not be maintained as the surgeon manipulates the instrument. If the contact pressure is too great, however, the surgeon may experience difficulty in advancing and properly controlling the instrument. Because larger instruments must expand the orifice to a greater degree, the contact pressure is consequently larger than for smaller instruments, and thus larger instruments may be more difficult to manipulate than smaller instruments. Accordingly, a need exists for an apparatus for forming a seal about an instrument inserted through a cannula that is capable of accommodating variously sized instruments while ensure a proper contact pressure.